Let's break down your requirements to real-world needs.
Proofing: with the KM C83hc you will not be able to produce contract proofs or validation prints, as the actual pigments' gamut is so much different to conventional (offset or digital) printers' gamut.
Invitation cards, business cards, leaflets: you may be able to print them if you don't need to match a former production's color.
Photo quality printing: this is what the hc is targeted to. You can produce outstanding prints especially if you use RGB source material (PDFs with RGB images embedded).
Banner printing: I don't know if the C83hc is able to print banners - it can be an option, or a paid upgrade (actually a software switch).